1. Field of the Invention
The present invention relates to aqueous ketone, ketone/aldehyde or urea/aldehyde resin dispersions, to a process for their preparation and to their method of use.
2. Discussion of the Background
The condensation of ketone, ketone/aldehyde and urea/aldehyde resins is known. They, for example, are described in Ullmann's Encyclopedia of Industrial Chemistry, VCH Verlagsgesellschaft mbH Weinheim 1993, Vol. 23, pp. 99-105, which is incorporated herein by reference. Such resins are generally insoluble in water.
DE-A 25 42 090 describes water-soluble compounds which carry sulfonic acid groups and which, in deviation from the novel process, are obtained in a conjoint condensation reaction from cycloalkanone, formaldehyde and alkali metal bisulfite.
DE7A 31 44 673 indicates water-soluble condensation products which are likewise obtained by conjoint reaction of ketones, aldehydes and compounds which introduce acid groups. Examples of the latter are sulfates and salts of amidosulfonic acid, of aminoacetic acid and of phosphorous acid.
According to DE-A 25 42 090 and DE-A 31 44 673, the products obtained include electrolyte (e.g. Na ions). However, such resins impair, inter alia, the corrosion protection afforded by coating systems.
DE-A 34 06 473 and DE-A 34 06 474, or EP-A 0 154 835, describe processes for preparing stable aqueous dispersions of urea/aldehyde resins or, ketone/(aldehyde) resins, in accordance with which the resin in the melt state or in a highly concentrated solution thereof, is dispersed in water in the presence of organic protective colloids and with or without the addition of emulsifiers. A disadvantage of this process is that the organic protective colloids and emulsifiers interfere with the use of the aqueous ketone/(aldehyde) and urea/aldehyde resins in the coating sector. The hydrophilic protective colloids and, if used, emulsifiers remain in the coating and thus render the coating sensitive to moisture. The coating swells under the action of moisture, loses hardness and suffers a loss of some of its corrosion protection effect.
Thus, it is an object of the present invention to develop a resin dispersion that is stable to hydrolysis and exhibits storage stability, without the disadvantages described above, while at the same time, maintaining properties customary for such resins.